Using well-characterized transcription factors from E. coli, we have constructed a synthetic genetic clock that produces a synchronous oscillating output in large populations of bacteria. In the proposed work, physiological and genetic approaches will be used to study the function of the synthetic clock, identify the important design features of the clock, and better insulate the synthetic genetic system from interference by other cellular signal transduction systems. Biochemical studies are proposed to measure the key parameters involved in clock function, and theoretical studies will develop models of clock function. Modeling will be used to determine the relationship of parameters affecting clock function, and to design better clocks. The predictions of theoretical studies will be tested experimentally. By comparing the results of theoretical studies and experimentation, we will elucidate the system design principals underlying the function of the synthetic genetic clock. These studies will explore the usefulness of using synthetic genetic systems to study system design principles, develop the technology for the construction of synthetic genetic systems, and advance our understanding of the temporal regulation of gene expression.